This invention relates generally to knot tying mechanisms, and specifically to a knotter for use in crop baling machines.
In conventional crop balers, hay, straw and similar crop material that has been previously cut, windrowed or swathed, is picked up from the ground by a pickup and fed in successive batches or charges into an elongated bale chamber in timed sequence with a reciprocating plunger. The plunger compresses the material into bales and, at the same time, gradually advances the bales toward the outlet of the bale chamber. As the bales reach a predetermined length as controlled by a metering device, a bale tying mechanism is actuated which wraps cord, twine or other flexible tying material around the bale and secures the ends of the material together.
Typically, a knotter is mounted on the bale chamber adjacent a slot therein, the knotter including a twine holder, a rotatable billhook, and various other component parts which interact to form a knot in the twine portions. During the baling operation, the leading strand of the twine is held by the twine holder and extends forwardly across a twine retainer finger and a billhook and then in front of the bale. The twine retainer finger supports the strand so that it does not bear forcefully against the billhook. A needle is involved in completing the encirclement of twine around the bale and, when advancing, the needle lays a trailing strand across the twine retainer finger, billhook and twine holder. A twine finger captures these strands of twine and positively positions the strands against the heel of the billhook. Thus, there are presented in a certain zone a pair of twine portions or strands lying alongside each other and these portions are twisted into a bight by the billhook and a portion thereof is pulled through the bight to form a double overhand knot. On completion of the operation of the knotter, the twine finger returns to the initial position. The removal of the tied knot from the billhook involves mechanical stripping by a movable member which normally embodies a knife operable to cut the twine from the twine supply so that the tied bale is complete in itself. The tying mechanism thus includes several components working in a precisely timed relationship so that theoretically the mechanism ties one knot for each bale and prepares the twine for the succeeding bale.
Those of skill in the art will generally agree that the knotter is one of the most complex components of a baler, and, therefore, one of the most difficult to understand and maintain. A great deal of research and experimentation has been, and still is on a continuing basis, undertaken by individuals and corporations in an effort to improve knotters and reduce their sensitivity. Examples of these efforts abound in the prior art. Recently, a novel knotter has been developed which exhibits exceptional structural simplicity and highly reliable operational characteristics. This new knotter is disclosed in co-pending Patent Application Ser. No. 916,313. The instant application is directed to improvements in the above-identified knot tying mechanism which substantially advance its performance characteristics.
In particular, the knotter disclosed in the 916,313 application includes a planar twine disc declined relative to the twine being presented to the twine-gripping area of the disc by the needle. This angle of twine presentation contributed to an incidence of mistie which, though acceptable, was not within a preferable range.